Recently, wind turbines have received increased attention as environmentally safe and relatively inexpensive alternative energy sources. With this growing interest, considerable efforts have been made to develop wind turbines that are reliable and efficient.
Generally, a wind turbine includes a rotor having multiple blades. The rotor is mounted to a housing or nacelle, which is positioned on top of a truss or tubular tower. Utility grade wind turbines (i.e., wind turbines designed to provide electrical power to a utility grid) can have large rotors (e.g., 30 or more meters in length). In addition, the wind turbines are typically mounted on towers that are at least 60 meters in height. Blades on these rotors transform wind energy into a rotational torque or force that drives one or more generators. Because of the size of the rotors, changes in wind direction and/or speed can result in significant loads on components of the wind turbine. Various techniques exist for reducing the load including, for example, generator torque control and/or controlling the pitch of the blades. In particular, high wind conditions increase the load on the blades such that the known wind turbine systems are required to cut-out or shutdown in order to reduce or eliminate damage to the blades or other wind turbine components.
Historically, wind turbines have been very small contributors to overall power generation to supply electrical grids. The low unit ratings (<100 kW) of previous generations of wind turbines and the uncertain availability of wind sources caused wind turbine generators to be ignored when power grid operators considered the security of the grid. However, wind turbine generators with ratings of 1.5 MW or more are now available. Furthermore, many power generation developers are installing wind turbine plants having large numbers of wind turbines, including plants having 100 or more wind turbines. The cumulative power available from wind farms with 1.5 MW wind turbine generators is comparable to a modern gas turbine generator. Accordingly, wind turbine are increasingly feasible sources of power for conventional power grids. Since current wind turbines have individual cut-out or shutdown wind speed tolerances, high wind events can cause the shut down of large numbers of wind turbines within the wind turbine plant, causing a severe loss of power to the grid and requiring start up of each of the shut-down wind turbines once the high wind event has passed. Wind turbines typically shut down during high wind events, e.g., when the wind speeds exceed about 20 m/s. The wind speed utilized to determine whether shut down is required is often averaged over a particular time frame and higher wind speeds can usually be tolerated for shorter periods of time. Accordingly, there are often two or more wind speeds that are used to determine the shut down threshold e.g., a 25 m/s averaged over 10 minutes and a 28 m/s averaged over 30 seconds and a 30 m/s averaged over 3 seconds. These shut down events unacceptably and suddenly decrease the power available to the grid as well as decrease the revenue provided by operating the equipment at higher wind speeds.
What is needed is a method and system for providing wind turbine plant control and monitoring to operate the wind turbines within the wind turbine plant within greater operational parameters during high wind conditions without damaging the wind turbine components or prematurely or unnecessarily shutting down the wind turbine.